The present invention is directed to improvements in multi-speed transmissions suitable for automotive uses. More particularly, the present invention is directed to a multi-speed transmission using paired helical gears wherein a compact transmission can be provided having increased power capacity compared to a conventional transmission.
Gear transmissions having pairs of helical gears mounted on a drive shaft for engagement with respective pairs of helical gears mounted on a driven shaft resulting in even load sharing amongst gears are disclosed in copending U.S. patent application Ser. No. 09/167,760 filed Oct. 7, 1998 which is a continuation application under 35 U.S.C. xc2xa7120 of pending application Ser. No. 09/021,622 filed Feb. 9, 1998, both of the preceding applications being entitled IMPROVEMENTS IN POWER SHARING GEAR SETS. The disclosures, including the disclosures of the specification and drawings of prior U.S. patent application Ser. No. 09/167,760 filed Oct. 7, 1998 and Ser. No. 09/021,622 filed Feb. 9, 1998 are hereby expressly incorporated by reference into this present application.
Paired helical gearing permits, as a practical matter, power sharing among multiple gears on a single shaft. Prior to the invention of paired helical gearing, very precise tolerances were required to successfully construct a transmission which had multiple gears on a common shaft. Therefore, prior to the invention of paired helical gearing, transmissions with multiple gears on a single shaft were for most purposes commercially impractical.
A major commercial application for paired helical gearing is transmissions that have constraints on the size of the diameter of gears due to space limitations, but which are also required to transmit significant power.
The present invention is directed to the use of paired helical gearing to provide for multi-speed transmissions suitable for automotive use. In the present application, transmissions for automotive use includes within its meaning, but is not limited to, uses in automobiles, trucks, farm equipment, earth moving equipment, ships, boats and the like.
It is an object of the present invention to provide a multi-speed automotive transmission that employs paired helical gearing.
It is also an object of the present invention to provide a multi-speed automotive transmission that is compact in size but has a high power capacity.
These and other objects of the present invention will become apparent from the following description and claims read in conjunction with the drawings.
The present invention is directed to a multi-speed transmission suitable for automotive-type uses. The transmission comprises an input drive shaft and idler shafts. Each speed of the transmission is provided by at least one pair of helical cut drive gears mounted on the drive shaft being engaged and mated by at least one pair of helical cut driven gears mounted on an idler shaft. The hand or the sense of the drive and driven helical cut gear pairs is selected so that upon engagement and mating of a selected pair of drive and driven helical cut gears for a given transmission speed, thrust forces are created to cause the pair of driven helical cut gears mounted on the idler shaft to move toward one another. The selected pair of driven helical gears mounted on the idler shaft also move together on the idler shaft to center themselves on the respective drive helical gears on the input drive shaft to balance the load and to provide for an approximate equal sharing of the transmitted load amongst gears.
For uses requiring large transmissions of power, for each speed of the transmission, two or more pairs of helical cut gears may be provided on the drive shaft for being engaged respectively by two or more pairs of helical cut gears provided on the idler shaft.
An output shaft is provided having mounted thereon one or more pairs of helical cut driven gears for rotating the output shaft. The idler shaft has mounted thereon one or more pairs of drive output helical cut gears rotated by the idler shaft and for engaging and mating the one or more helical gear pairs mounted on the output shaft for transmission of power to the output shaft.
In the drawings forming part hereof:
FIG. 1 is a schematic view of one embodiment of an automotive transmission in accordance with the present invention illustrating a four speed transmission using for each speed of the transmission one pair of paired helical gears on an input drive shaft and one pair of paired helical gears on an idler shaft.
FIG. 2 is a schematic view of another embodiment of an automotive transmission in accordance with the present invention illustrating a two speed transmission using for each speed of the transmission two pairs of paired helical gears on an input drive shaft and two pairs of paired helical gears on an idler shaft.
FIG. 3 is a schematic cross-sectional view along line 3xe2x80x943 of FIG. 1.
FIG. 4 is a schematic cross-sectional view along line 4xe2x80x944 of FIG. 2.
FIG. 5 is a schematic view of one embodiment of a shifting mechanism suitable for use with the transmission of the present invention.
FIG. 6 is a schematic side view of a shifting fork used in the shifting mechanism illustrated in FIG. 5.